The present invention relates to a feature for on-road vehicles that enables a precautionary action, such as warning the vehicle driver or braking, accelerating, or maneuvering the vehicle, to be taken in response to an upcoming condition on the road network.
Advanced driver assistance systems (“ADAS”) have been developed to improve the comfort, efficiency, and overall satisfaction of driving. Examples of advanced driver assistance systems include adaptive headlight aiming, adaptive cruise control, and adaptive shift control, as well as others. Some of these advanced driver assistance systems use a variety of sensor mechanisms in the vehicle to determine the current state of the vehicle and the current state of the roadway in front of the vehicle. These sensor mechanisms may include radar and vision-oriented sensors, such as cameras. Some advanced driver assistance systems also use digital map data. Digital map data can be used in advanced driver assistance systems to provide information about the road network, road geometry, road conditions and other items associated with the road around the vehicle. Digital map data is not affected by environmental conditions, such as fog, rain or snow. In addition, digital map data can provide useful information that cannot reliably be provided by cameras or radar, such as speed limits, traffic and lane restrictions, etc. Further, digital map data can be used to determine the road ahead of the vehicle even around corners or beyond obstructions. Accordingly, digital map data can be a useful addition for some advanced driver assistance systems.
U.S. Pat. Nos. 6,405,128 and 6,735,515 describe methods for using map data to provide driver assistance features. These patents describe formation of an electronic horizon for a vehicle. The electronic horizon contains a versatile, structured data representation of the road network around a vehicle that extends from the current position of the vehicle along accessible roads out to a threshold (i.e., the electronic horizon). The electronic horizon is recalculated as the vehicle moves. These patents also describe how an electronic horizon can be used, e.g., in conjunction with sensors in the vehicle, to provide curve warnings, intersection warnings, adjust transmission settings, and so on.
Included among the features described in these patents are the determination of a route-based path and the determination of a most-likely path. An electronic horizon may include multiple paths leading from a vehicle's current position. In the situation in which a vehicle driver is being provided guidance to follow a calculated route to a destination, part of the calculated route will coincide with one of the paths in the electronic horizon. This path may be identified as the route-based-path and data indicating the route-based-path may be stored with the electronic horizon data structure. Even if a vehicle is not following a calculated route to a destination, one of the paths from the vehicle's current position may be determined as the most-likely-path, and other feasible paths may be assigned lower probabilities of occurrence. The most-likely-path and lower probability paths are determined based on identifying the most likely maneuvers a driver may be expected to choose at each upcoming intersection within the electronic horizon. Determining the most likely maneuver that a vehicle driver may choose to take at an intersection is based on a predetermined ranking of all possible maneuvers at the intersection, taking into account turn angles, road function classes, traffic signals, speed limits, and other stored information about the road network.
The inventions disclosed in the '128 and '515 patents provide useful features. However, there exists room for further improvements. Accordingly, it is an objective to provide additional advantages when using a data model of the road network around a vehicle.